EP0031746B1 - Schaltung zur Demodulation eines digital modulierten Signals und eine solche Schaltung enthaltender Empfänger - Google Patents

Schaltung zur Demodulation eines digital modulierten Signals und eine solche Schaltung enthaltender Empfänger Download PDF

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Publication number
EP0031746B1
EP0031746B1 EP80401765A EP80401765A EP0031746B1 EP 0031746 B1 EP0031746 B1 EP 0031746B1 EP 80401765 A EP80401765 A EP 80401765A EP 80401765 A EP80401765 A EP 80401765A EP 0031746 B1 EP0031746 B1 EP 0031746B1
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EP
European Patent Office
Prior art keywords
circuit
carrier
signal
frequency
demodulation
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
EP80401765A
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English (en)
French (fr)
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EP0031746A3 (en
EP0031746A2 (de
Inventor
Jean-Pierre Dehaene
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Thales SA
Original Assignee
Thomson CSF SA
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Publication date
Application filed by Thomson CSF SA filed Critical Thomson CSF SA
Priority to AT80401765T priority Critical patent/ATE8556T1/de
Publication of EP0031746A2 publication Critical patent/EP0031746A2/de
Publication of EP0031746A3 publication Critical patent/EP0031746A3/fr
Application granted granted Critical
Publication of EP0031746B1 publication Critical patent/EP0031746B1/de
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/10—Frequency-modulated carrier systems, i.e. using frequency-shift keying
    • H04L27/14—Demodulator circuits; Receiver circuits

Definitions

  • the present invention relates to a circuit for the demodulation of a modulated signal originating from the frequency modulation of a carrier by digital information and having a line at the carrier frequency, said circuit comprising an adder circuit receiving on a first input the modulated signal.
  • Such circuits include a phase-locked loop which provides the modulating information (phase lock loop in the Anglo-Saxon literature). These loops consist of a phase comparator which receives the information to be demodulated on one of its inputs and whose output is connected, through a low-pass filter and an amplifier, to the control input. a variable oscillator circuit; the output of the oscillator is connected to the other input of the phase comparator and the demodulated signal is received at the output of the amplifier.
  • Such loops must be broadband since they must allow the entire frequency band of modulating information to pass; these loops are therefore difficult to achieve and, therefore, expensive.
  • the document FR-A-2 302 640 describes a circuit for the demodulation of a modulated signal originating from the frequency modulation of a carrier by digital information and having a line at the carrier frequency; this demodulation circuit comprises an adder circuit receiving, on a first input, the modulated signal and, on a second input, a locally produced fixed frequency signal.
  • this demodulation circuit there is addition to the modulated signal, of frequency F a or F 1 ' of the signal at fixed frequency, of frequency this fixed frequency signal, because it is produced by a simple local oscillator, is incoherent with respect to the received signal, that is to say that its phase is not linked to the phase of the received carrier.
  • the information is detected by means of two filters tuned respectively to the frequencies F o and F "by a digital demodulator; however, such a demodulator cannot be used for the demodulation of analog information because it is not linear in
  • the present invention aims to avoid the abovementioned drawbacks and to allow the use of certain analog signal receivers for the reception, under good conditions, of modulated signals originating from the frequency modulation of a carrier by a digital information with a line at the carrier frequency.
  • a circuit of the type indicated at the beginning of this text is characterized in that it also includes carrier recovery means, receiving the modulated signal and having an output coupled to a second input of the adder circuit and in that the output of the adder circuit is coupled to the input of a linear frequency demodulator at least in the frequency band necessary for the transmission of the modulated carrier.
  • FIG. 1 represents an input circuit, 1, which receives high frequency signals, carrying information.
  • This input circuit which includes a frequency transposition device, delivers signals at intermediate frequency.
  • the signals received come from the frequency modulation of a carrier at the frequency F by binary signals representing the information to be transmitted.
  • these binary signals are rectangular signals of duration the logical value "1" is represented by a signal of amplitude V + v during the first and last quarters of the duration T, and of amplitude Vv during the second and third quarters of the duration T; the logic value "0" is represented by a signal of amplitude Vv during the first and last quarters of duration T and of amplitude V + v during the second and third quarters of duration T.
  • these amplitude signals V + v and Vv are transformed respectively into signals at the frequency F + dF and F-dF.
  • the value dF is chosen equal to f so that, during the times where the bits "1" and "0" in the figure 2 have a constant amplitude, the phase variation, to which the corresponding frequency hopping is equivalent, results in a phase difference of with respect to the unmodulated signal, that is to say to the carrier at frequency F.
  • FIG. 3 is a trigonometric representation of the variation of the phase p of the modulated carrier represented by a vector OM of which the end M travels, at a constant speed, from at a trigonometric circle of axes OX and OY.
  • FIG. 4 which can easily be deduced from FIG. 3, is a representation of the variation of the abscissa OX and of the ordinate OY of the point M representative of the phase of the modulated signal. Whether the modulating binary element is a "1" or a "0", the variation on the abscissa is the same while the variation on the ordinate is different: curve marked “1” relative to the binary element "1” and curve identified " 0 "relating to bit” 0 ".
  • the amplified line R (vector 0'0, FIG. 6) added to the intermediate frequency signal (vector OM, FIG. 6), that is to say to the received modulated carrier, gives a new signal (vector O'M , Figure 6) where the phase modulation o 'is compressed relative to that, cp, of the modulated carrier received.
  • the output signal of the adder corresponds to the signal with reinjected carrier which was discussed during the description of FIG. 6.
  • This signal is applied to the input of a linear frequency demodulator, 7, of the such as a discriminator demodulator, the discrimination threshold of which is thus artificially improved for the modulated signal supplied by the input circuit 1.
  • the invention is not limited to the case of the example described, this is how the carrier recovery circuit according to FIG. 1 (elements 3 to 6) can be replaced by a bandpass filter centered on the frequency. carrier of the modulated signal received.
  • the circuit according to the invention can be used for the demodulation of any signal modulated by digital information and whose spectrum has a line at the carrier frequency.
  • the circuit according to the invention is more specifically intended to equip a radio receiver with a link by analog radio-relay systems when using this link for the temporary transmission of digital information; a simple switching device then makes it possible to connect the output of the input circuit 1 of FIG. 1 to the input of the demodulator 7, either as indicated in FIG. 1, or by a simple connection.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Digital Transmission Methods That Use Modulated Carrier Waves (AREA)
  • Noise Elimination (AREA)
  • Circuits Of Receivers In General (AREA)
  • Selective Calling Equipment (AREA)

Claims (4)

1. Schaltung zur Demodulation eines modulierten Signals, das durch Frequenzmodulation einer Trägerschwingung durch eine digitale Information entsteht und eine Frequenzlinie bei der Trägerfrequenz aufweist, mit einer Addierschaltung (2), die an einem ersten Eingang das modulierte Signal empfängt, dadurch gekennzeichnet, daß sie ferner Mittel zur Wiedergewinnung der Trägerschwingung (3, 4, 5, 6) enthält, welche das modulierte Signal empfangen und einen Ausgang aufweisen, der an einen zweiten Eingang der Addierschaltung angekoppelt ist, und daß der Ausgang der Addierschaltung an den Eingang eines Demodulators (7) angekoppelt ist, der wenigstens in dem für die Übertragung der modulierten Trägerschwingung erforderlichen Frequenzband frequenzlinear ist.
2. Schaltung zur Demodulation eines Signals nach Anspruch 1, dadurch gekennzeichnet, daß die Mittel zur Wiedergewinnung der Trägerschwingung in Reihenschaltung eine Phasenkomparatorschaltung (3) mit einem ersten, das modulierte Signal empfangenden Eingang, ein Tiefpaßfilter (4), einen Verstärker (5) und einen variablen Oszillator (6) enthalten, der durch den Verstärker gesteuert wird und dessen Ausgang mit dem zweiten Eingang der Phasenkomparatorschaltung und mit dem Ausgang der Trägerschwingungs-Rückgewinnungsmittel verbunden ist.
3. Schaltung zur Demodulation eines Signals nach Anspruch 1, dadurch gekennzeichnet, daß die Trägerschwingungs-Rückgewinnungsmittel ein Bandpaßfilter enthalten, dessen Durchlaßband auf die Trägerfrequenz zentriert ist, und daß das Filter das modulierte Signal empfängt, während sein Ausgang an den Ausgang der Trägerschwinnungs-Rückgewinnungsmittel angeschlossen ist.
4. Funkempfänger, dadurch gekennzeichnet, daß er eine Schaltung zur Demodulation eines Signals nach einem der vorstehenden Ansprüche enthält.
EP80401765A 1979-12-27 1980-12-09 Schaltung zur Demodulation eines digital modulierten Signals und eine solche Schaltung enthaltender Empfänger Expired EP0031746B1 (de)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT80401765T ATE8556T1 (de) 1979-12-27 1980-12-09 Schaltung zur demodulation eines digital modulierten signals und eine solche schaltung enthaltender empfaenger.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR7931804 1979-12-27
FR7931804A FR2472878A1 (fr) 1979-12-27 1979-12-27 Circuit pour la demodulation d'un signal module par une information numerique et recepteur comportant un tel circuit

Publications (3)

Publication Number Publication Date
EP0031746A2 EP0031746A2 (de) 1981-07-08
EP0031746A3 EP0031746A3 (en) 1981-07-22
EP0031746B1 true EP0031746B1 (de) 1984-07-18

Family

ID=9233209

Family Applications (1)

Application Number Title Priority Date Filing Date
EP80401765A Expired EP0031746B1 (de) 1979-12-27 1980-12-09 Schaltung zur Demodulation eines digital modulierten Signals und eine solche Schaltung enthaltender Empfänger

Country Status (6)

Country Link
US (1) US4365205A (de)
EP (1) EP0031746B1 (de)
JP (1) JPS56102149A (de)
AT (1) ATE8556T1 (de)
DE (1) DE3068626D1 (de)
FR (1) FR2472878A1 (de)

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS58104578A (ja) * 1981-12-16 1983-06-22 Sony Corp テレビジヨン受像機の音声回路
NL8502967A (nl) * 1985-09-19 1987-04-16 Philips Nv Hoekdemodulator.
US6144253A (en) * 1997-10-27 2000-11-07 Elsag International N.V. Digital FSK demodulator

Family Cites Families (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB201591A (en) * 1922-03-28 1923-07-30 Ernest Yeoman Robinson Improvements in systems of reception for modulated wave telegraphy and telephony
CH244477A (de) * 1943-09-29 1946-09-15 Ges Foerderung Forschung Technische Physik Eth Zuerich Verfahren zum Empfang von amplitudenmodulierten elektrischen Signalen mit reduziertem Träger.
FR1259477A (fr) * 1960-03-16 1961-04-28 Electronique & Physique Perfectionnements aux récepteurs pour certaines émissions radioélectriques sans porteuse
GB1022598A (en) * 1963-10-18 1966-03-16 Nat Res Dev Improvements in or relating to receivers for binary-coded signals
US3525945A (en) * 1968-08-14 1970-08-25 Communications Satellite Corp System for reconstituting a carrier reference signal using a switchable phase lock loop
FR2302640A1 (fr) * 1975-02-25 1976-09-24 Thomson Csf Systeme de transmission d'informations utilisant une modulation par deplacement de frequence
CA1115789A (en) * 1977-05-12 1982-01-05 Richard P. Scott Phase shift keyed systems

Also Published As

Publication number Publication date
ATE8556T1 (de) 1984-08-15
FR2472878A1 (fr) 1981-07-03
US4365205A (en) 1982-12-21
JPS56102149A (en) 1981-08-15
FR2472878B1 (de) 1982-06-11
JPH0249066B2 (de) 1990-10-29
EP0031746A3 (en) 1981-07-22
EP0031746A2 (de) 1981-07-08
DE3068626D1 (en) 1984-08-23

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